Synthesis of Pentafluorophenyl Silver by Means of Lewis Acid Catalysis: Structure of Silver Solvent Complexes

The synthesis and structure of lithium and silver tetrakis(pentafluorophenyl)borate salts have been studied in different solvents ranging from polar (CH2Cl2, diethyl ether) to nonpolar (toluene, pentane). While Li[B(C6F5)(4)] is stable in all studied solvents and crystallizes with four ether molecules from ether and with two toluene molecules from toluene, the silver salt is only stable when the Ag+ ion is strongly coordinated such as in [Ag(toluene)(3)][B(C6F5)(4)] or [Ag(Et2O)(3)][B(C6F5)(4)]. In weakly coordinating solvents such as CH2Cl2 Ag[B(C6F5)(4)] decomposes, yielding AgC6F5 and B(C6F5)(3). The overall process of the AgC6F5 synthesis starting from B(C6F5)(3) and LiC6F5 can formally be regarded as a B(C6F5)(3)-catalyzed reaction. The salt [Ag(toluene)(3)][B(C6F5)(4)] presents an easily accessible, ether-free, stable silver salt of the [B(C6F5)(4)](-) anion. All compounds have been fully characterized.